Low network throughput on i.MX28

[Jörg Krause]

Hi Lothar,

Am 13. Oktober 2016 08:48:07 MESZ, schrieb "Lothar Waßmann" <LW at KARO-electronics.de>:
>Hi,
>
>On Thu, 13 Oct 2016 01:09:13 +0200 Jörg Krause wrote:
>> Hi,
>> 
>> I am using a custom i.MX28 board similar to the i.MX28-EVK. For Wi-Fi
>> the board assembles a BCM43362 from Broadcom and for Ethernet a
>> LAN8720A from Microchip. The board is running mainline Linux 4.7.
>> 
>> While both, wireless and wired network interfaces work, the TCP
>> throughput measured with iperf is low.
>> 
>> The bandwith for Ethernet is between 20-30 MBits/sec and for WLAN is
>> about 4-5 MBits/sec.
>> 
>> There exists an Application Note "i.MX28 Ethernet Performance on
>> Linux" [1] which shows a bandwith of > 60 MBits/sec. A user an the
>NXP
>> forum [2] told he achieved 20 MBits/sec with some Qualcom chip.
>> 
>> Note, that these values are most probably measured with the legacy
>> Linux Kernel 2.6.35 from NXP.
>> 
>> Does anybody has done throughput tests on i.MX28 with mainline
>Kernel?
>> If so, what are the results? What might be the bottleneck?
>>
>
>This is the iperf output on a TX28 with current mainline kernel
>(4.8.0-rc5):
>------------------------------------------------------------
>Client connecting to 192.168.100.1, TCP port 5001
>TCP window size: 43.8 KByte (default)
>------------------------------------------------------------
>[  3] local 192.168.100.56 port 60325 connected with 192.168.100.1 port
>5001
>[ ID] Interval       Transfer     Bandwidth
>[  3]  0.0-10.0 sec  57.5 MBytes  48.2 Mbits/sec
>
>You might check your kernel DEBUG configs (especially
>CONFIG_DEBUG_PAGEALLOC).

Thanks for sharing the iperf output. What LAN transceiver does the TX28 has assembled?

I checked the config and is has no DEBUG_PAGEALLOC enabled and no DEBUG options related to network.

Best regards
Jörg Krause